Organizations and enterprises generate significant revenue by delivering data communication services based on quality of service (QoS), which has become an important metric upon which billing is based. In order to improve or maintain QoS, services such as leased lines, virtual leased lines (VLLs), virtual private networks (VPNs), virtual private LAN services (VPLS), and others provide dedicated data communication systems. These systems provide a “dedicated” path tunnel, which can be a virtual circuit (VC) for data communication between two or more customer networks that are not locally connected.
One typical approach is to define label switched paths (LSPs) through which traffic to a particular destination or set of destinations serviced by a particular provider edge (PE) router may be tunneled. Where multiple locations may need to be able to send traffic to the destination, a multipoint-to-point (sometimes referred to herein by the abbreviation “MP2P”) LSP may be defined. In MPLS (multi-protocol label switching), an LSP is typically MP2P. LSPs can also be used for point-to-point (P2P) applications and typically result from the use of label switching and the unidirectional nature of LSPs. In such a MP2P LSP, a plurality of defined paths from the originating PE's associated with ingress tunnel endpoints converge onto a single path entering the destination PE. A problem arises, however, in that the destination PE must have a way of learning the identity of the originating PE and associating that PE with the source MAC address of a received packet, e.g., in order to know how to route traffic sent to that source MAC address. When MPLS or MPLS versions of existing protocols (e.g., RSVP-TE, LDP, MP-BGP, etc.) are used to implement an LSP, the destination (receiving) PE does not have any way of knowing which PE originated the packet, as each node along the LSP uses its own label to forward packets to the next node, with the result that the receiving PE can identify through the primary label only the core device that forwarded the packet to the receiving PE along the last hop or leg of the LSP.
Conventional multipoint-to-point implementations require overlays of virtual tunnels to resolve this problem. In particular, in one typical approach a separate VC label is assigned per source PE for each service. In general, the typical approach solves a source identification problem and the multiplexing of traffic for different VPNs using the same transport. However, it does not reduce the number of labels. This approach is disadvantageous because of the overhead and complexity associated with assigning, managing, and routing packets using such a large number of labels. To quantify the shortcoming, if a separate VC label is assigned for each of “n” PE devices or nodes associated with a particular customer or service, for example, the number of labels per service would be on the order of n2 (specifically n(n−1)), as each node would be required to have a separate virtual point-to-point circuit to each other node. By contrast, if the destination PE had a way of identifying the originating PE without requiring that a separate VC label be assigned for each PE for each service, each of the n PE devices would require only one label per service, so that only n labels would be required.
Thus, it would be useful for a solution to solve how to determine a source station's address without creating an additional layer or mesh of tunnels for a MP2P LSP.